Field of the Invention
The present invention relates to a method for producing a polycrystalline SiC wafer by irradiating a polycrystalline SiC ingot with a laser beam.
Description of the Related Art
Power devices, LEDs, and so forth are formed on a surface of a wafer including hexagonal single crystal SiC as a material in such a manner as to be marked out by planned dividing lines, and are used for various pieces of electrical and electronic equipment such as mobile phones and personal computers through dividing into individual device chips by a cutting apparatus and a laser processing apparatus. The hexagonal single crystal SiC wafer from which devices are formed is generated by slicing a single crystal SiC ingot by a wire saw generally and the front and back surfaces of the sliced wafer are polished to be finished into mirror surfaces (for example, refer to Japanese Patent Laid-open No. 2000-094221).
Meanwhile, for manufacturing of the hexagonal single crystal SiC wafer, which is expensive, the following method has been proposed as a method for reducing the manufacturing cost. First, a polycrystalline SiC ingot, which is more inexpensive than the hexagonal single crystal SiC, is formed and a flat polycrystalline SiC wafer is cut out with a thickness of about 300 μm for example from this polycrystalline SiC ingot. Then, to the upper surface of the cut-out polycrystalline SiC wafer, a hexagonal single crystal SiC wafer in which a separation layer is formed through implantation of hydrogen ions to a predetermined thickness (for example, thickness of 1 μm) and so forth is bonded. Then, the hexagonal single crystal SiC wafer is separated, with a hexagonal single crystal SiC layer having a thickness of 1 μm left on the upper surface of the polycrystalline SiC wafer. Thereby, a wafer that includes the polycrystalline SiC wafer as the base material and has a front surface composed of the hexagonal single crystal SiC wafer is formed (for example, refer to Japanese Patent Laid-open No. 2014-216555).